A block assembly includes integral connection mechanisms specifically designed for incorporation into engineered retaining walls. A first control signal is received from a first network node and a second control signal is received from a second network node. An ultrasonic transducer device includes an ultrasonic transducer and a coupling element coupled to the transducer for disposition between the transducer and a surface of a structure. The electrode assembly defined to impart an electrical contact to the substrate when present and held by the pair of clamps. The second protection unit protects the first program while the execution unit is executing the second program. The emergency flight plan could cause the aircraft to fly to a sparsely populated area and enter a holding pattern, or it could cause the aircraft to land in a sparsely populated area or at an airport using an autoland system.